Storage capacities of hard disc drives (HDDs) have generally increased over time due in part to increases in areal density. Increases in HDD capacity driven by increased areal density, while reducing cost, can reduce effective input/output (I/O) performance (i.e., I/O access speed per unit capacity) if the read/write assembly remains substantially the same. For example, a relatively large write operation (e.g., a rebuild of a failed volume of a disc drive array) can take an unacceptable quantity of time at the aerial densities now found in HDDs.
One way to increase I/O performance is to utilize multiple actuator arms with associated read/write heads simultaneously, and independently running in parallel. Such parallelism can increase the rate of input/output operations (IOPS) and thereby improved I/O performance. Further, use of independently operating actuator arms and their associated read/write heads can provide improved read/write flexibility for a system designer. For example, an HDD can be configured with zones having different levels of throughput and capacity, and each of multiple read/write heads running in parallel can be operated in different modes to improve throughput in some zones while improving capacity (or another performance parameter) in other zones. However, multiple read/write heads running in parallel can cause coupling issues between the read/write heads, which may negatively affect HDD performance, including but not limited to introducing an unacceptable quantity of read/write errors.